Electromechanical Wave Imaging (EWI) is an entirely non-invasive, ultrasound-based imaging method capable of mapping the electromechanical wave (EW) in vivo, i.e., the transient deformations occurring in response to the electrical activation of the heart. Achieving the optimal imaging frame rates necessary to capture the EW in a full-view of the heart poses a technical challenge due to the limitations of conventional imaging sequences, in which the frame rate is low and tied to the imaging parameters. To achieve higher frame rates, EWI is typically performed in multiple small regions of interest acquired over separate heartbeats which are then combined into one view. Yet, the frame rates achieved remain suboptimal, because they are tied to the imaging parameters rather than being optimized to image the EW. More importantly, the reliance on multiple heartbeats precluded the study from application in non-periodic arrhythmias such as fibrillation.
Acoustic radiation force has been used to induce motion in living tissue to allow the non-invasive characterization of tissue properties in a live host. In U.S. Patent Publication No. 2007/0276242 to Konofagou, which is incorporated herein by reference as if set forth in its entirety herein, Konofagou describes systems, methods and apparatus which are used to focus ultrasound in a selected volume of tissue remote from an externally applied transducer to generate motion in the tissue. The techniques and devices of this reference may be employed in the new subject matter described in the disclosure below.
Tissue engineering methods devices and system that employ hydrogels incorporating microbubbles have been described in PCT Patent Publication No. WO 2011/028690 (PCT/US2010/047263) to Borden, et al., which is incorporated herein by reference as if set forth in its entirety herein. In this application, Borden, et al., describe tissue scaffolds with microbubbles and seeded with cells. The bubbles may be gas-filled to alter the mechanical properties of the tissue scaffold, for example, by making it compressible. Also, the microbubbles can ameliorate the movement (as by diffusion) of fluids such as perfusate through the tissue scaffold. Microbubbles of a suitable form are described in PCT/US2010/047263.
Tissue engineering requires the cultivation and development of cells in realistic environments. For example, some kinds of tissues may require mechanical stimulation or signaling in order to develop properly. Also, thick three-dimensional structures may make it difficult for chemical signaling and nutrient perfusion.